where is glow plug relay switch?
 

Can anyone tell me where is the glow plug relay switch situated on a 1976 w115 240d?

the 115 had a relay?
I was under the impression that they used the gorilla knob...
if not, then the relay should be under the dash up by the brake pedal assembly/steering shaft. and the switch to energize the relay should be in the ignition assembly.

Its called a gorilla knob? Well, my 115 has a gorilla knob. So if there's no relay, is there 80 amps running through the dashboard to power the glowplugs? If not, how does that system work, and what makes that thing start to glow behind the little plastic grill on the dash (and does it burn out)?

should be 50 amps... series plugs use less power.
I do not know where the fuse would be. the glow behind the salt shaker is a resistor element, so I suppose it could indeed fail...